Asphalt pavement



May 19, 1953 J. c. ROEDIGER ASPHALT PAVEMENT Filed Jan. 5. 1949 Patented May 19, 1953 ASPHALT PAVEMENT Joseph Carl Roediger, Brooklyn, N. Y.assig'n`or` to Standard Oil Development Company, a corporation of Delaware Application January 3, 1949, Serial No. 69,032

(Cl. S14- 9) 3 Claims. 1

This invention relates to improvements in as,- phalt pavements for application over impervious bases, such as concrete and relates particularly to asphalt pavements with surfaces that are capable of with standing long exposure to weather before the critical hardness is reached that results in cracking. a

In the application of asphalt-aggregate paving mixtures over impervious bases, such as a concrete pavement, it has Ibeen found that water collects in the layer of pavement adjacent to the impervious concrete base as it cannot drain downward through the base. Long contact of this entrapped Water with the asphalt mixture gradually induces the removal or stripping of the asphalt from the mineral particles. This action progressively proceeds upward through the asphalt mixture until failure occurs due to cracking and crumbling of the top surface of the pavement. During this progressive upward stripping action of the water, the top of the exposed pavement remains in a satisfactory unstripped condition.

Present art shows that the stripping actionof the water can be overcome by the incorporation of certain asphalt wetting agents in the asphalt prior to application. Wetting agents of this type are generally heavy metal soaps, high molecular weight organic amines or nitrogenous base materials, or combinations of amine with organic acids. Another method involves pretreatment of the mineral aggregate with these wetting agents prior to application of the normal, untreated asphalt. However, these additives increase the cost of the nal asphalt pavement and it is economic to reduce the quantities used to the minimum level required to meet the average stripping action encountered in road construction. Under the severe stripping conditions encountered with an asphalt pavement over concrete, higher than normal wetting agent quantities must be used to attain satisfactory results, and the resultant added cost is frequently uneconomic.

It is also known that the rate of stripping of an asphalt coating decreases as the consistency of the asphalt is increased. For example, a 100 g./ sec/at 77 F.- 41/50 penetration grade asphalt strips less from a given coated aggregate than the same aggregate coated with an asphalt of 100 g./5 sec/at 77 F. 85/100 penetration, for the same duration of water exposure. However,

the pavement laid with the 100 g./5 see/77 F. 41/50 penetration asphalt is more prone to crack on aging than one made with the softer 100` g./5 sec/77 F. 85/100 penetration grade. Due to the action of sunlight, air and moisture, the asphalt in a pavement hardens with continued exposure, which is most pronounced at the top surface of the pavement where more ready access of the elements is possible;

begins to crack, usually from the top surface downward.

The accompanying` drawing depicts a crosssection of a road constructed in accordance with a preferred embodiment of the present invention.

is in need of resurfacing. It is also contemplated that this course will be primed with one of the standard asphalt primers before any asphaltic lcourses are applied on it.

Immediately above the foundation course `is lower asphaltic course 3 composed of particles of aggregate 4, an asphalt binder -5 and an asphalt wetting agent. The asphalt binder preferably has a penetration value of 40-60 and contains an anti-stripping asphalt wetting agent in an amount 50-100 percent greater than the amount found to be the minimum level for the aggregate being used. In addition, the asphalt binder maycon-` stitute from 4% to 12% by weight of the course.

Upper asphaltic course 6 is applied directly above lower course 3 and is composed of an asphalt binder 8 and particles of laggregate l. The asphalt binder in this course has a penetration value in the range of to 100, contains no wetting agent, and may constitute from about 9.5 to 12% by weight of the course. The softer asphalt in this course will be capable of longer exposure to the weather before the critical hardness, resulting in cracking, is reached.

In summary, this combination paving construction consists of: 1) a lower course made. with a relativelyhard asphalt containing more than the normal amount of asphalt wetting agent in order to attain maximum resistance to the stripping When the weathered as-` phalt reaches a critical hardness, the mixture` The present invention, then, concerns an aS- phaltic pavement structure that possessesim-` 3 action of water, and (2) an upper course made with a softei` asphalt without wetting agent in order to attain maximum resistance to cracking in a region Where the stripping action of water is negligible. An economic benefit also results since the costly asphalt wetting agent shall only .be used. in the region wheresevere stripping action results;

The thickness of the layers used may be varied extensively depending upon certain trafic condi. tions. Where trafc is relatively heavy, a heavier under layer is used and the thickness of the center layer may be increased, The. thickness of both layers may be the sarnelor greater in 'one layer than the other. Likewise thecoinp'o'sitions are varied; for example, if a smooth top layer is desired the amount of asphalt added to the mineral aggregate is increased.

The bottom course maybe a 2" layer of graded aggregate asphaltic concrete prepared with a harder asphalt (4D/60v penetration)y than is normally specied, and containing 2 percent byl weight in the asphalt of a metallic soap wetting agent, lead naph'then-ate. The top course would be a conventional sheet asphalt surface course of 1".

Bottom Courser Top Cou-rse Thickness 2"` 1 i. Combined Aggregate plus Y Fillerk Total Percent Sievse lSlize: P sing Penetration 77 F./100 g./5 sec. 3

40/50 85/100 @un 6.0-8.0 9 5-12. 'o Lead Naphthenate 2 2. 0 None 1 Asphalt cement in pounds perv 100 pounds of-,aggregata 2 Wettiug agent in pounds per 100 pounds of asphalt.

Conventional methods are used for the preparation of the hot mixes, and their application to the road'. Various conventional combinations of high type base course mixtures and surface course mixtures can be used. Other asphaltv to hot mix, hot laid paving` mixtures, but can also.

be employed to the so-called cold coated mixtures made by plant mix methods-such as the macadam aggregate, dense graded aggregate CST types and such proprietary mixtures as Amesite.

The wetting agents used according to this invention are lauryl amine plus fatty acid, lead naphthenate, iron naphthenate, lead oleate, iron oleate, imidazoline, heptadecylimidazoline, heptadecylimidazoline with fatty acid, tall oil, imidazoline plus fatty acid, and a sulifonic acid salt of an adhesive selected from the group consisting of cation-active organic derivatives of ammonia containing at least one lipophilic radical directly attached to a nitrogen atom of said ammona 4derivative by means of a nitrogen to oarbon bond, etc.

What is claimed:

l. An asphalt structure consisting of a substantially water-impervious pavement foundation, a lower asphalt course consisting of a relatively Yhard asphalt having a 100 g./5 sec/77 F. penetration of 40-60, mineral aggregate and an asphalt wetting agent, and an upper asphalt course consisting of mineral aggregate and an asphalt having a 160 g./5 seo/77 F. penetration of '7G-100.

2. An improved age and wear-resistant asphalt pavement vstructure comprising a foundation course consisting of concrete, a lower asphalt course consisting of 4-12% of asphalt having a 100 g./5 sec/77 F. penetration of 4li-60, a minera-l aggregate and l-5% based on the asphalt of an asphalt wetting agent, and an upper asphalt course consisting of a mineral aggregate and 9.5'- 12'% of an asphalt having a 1GO g./5 sec/77 F. penetration of 85-100.

3. An improved age and Wear resistant asphalt .pavement structure vcomprising a foundation course consisting of concrete, a lower asphalti'c concrete course consisting of 6 to' 8% of asphalt having a 169 g./5 sec/77 penetration of 40 to 50, a mineral aggregate and about 2% based on the asphalt lof an asphalt wetting agent and an upper sheet asphalt course consisting of la mineral aggregate and 91/2 to 12% of an asphalt liaiing a 100 g./5 sec/77 F. penetration of 85 JOSEPH CARL ROEDIGER.

References Cited in the le of this patent UNITED STATESy PATENTS.

Number Name` Date Re. 16,799 Burdge Nov. 29, 1927 1,082,722 Alexander Dec. 30, 19:13 1,845,405 Finley Feb. 15, w32 2,332,260' Roediger Oct.' 19, 1948 2,339,853 Hemmer Jan. 25, 1944 2,342,861 Hemmer Feb. 29, 1,944

FOREIGN PATENTS Number Country Date 23,881 Australia Dec. 10, 1936 of 1935 

1. AN ASPHALT STRUCTURE CONSISTING OF A SUBSTANTIALLY WATER-IMPERVIOUS PAVEMENT FOUNDATTION, A LOWER ASPHALT COURSE CONSISTING OF RELATIVELY HARD ASPHALT HAVING A 100 G./5 SEC./77* F. PENETRATION OF 40-60, MINERAL AGGREGATE AND AN ASPHALT WETTING AGENT, AND AN UPPER ASPHALT COURSE CONSISTING OF MINERAL AGGREGATE AND AN ASPHALT HAVING A 100 G./5 SEC./77* F. PENETRATION OF 70-100. 